Catalytic hydrogenolysis of cycloaliphatic alcohols, ketones, and aldehydes



Patented June 3, 1952 CATALYTIC HYDROGENOLYSIS OF CYCLO- ALIPHATIC ALCOHOLS,

ALDEHYDES V KETONES, AND

John E. Castle, New Castle, and Benjamin W. Howk, Wilmington, Del. assignors to E. I. du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware No Drawing. Application September 20, 1948.

Serial No. 50,238

(5 Claims. (Cl. 260-666) This invention relates to hydrogenolysis processes and more particularly to the catalytic hydrogenolysis of certain classes of oxygenated compounds.

It is known that hydrogenolysis occurs readily when oxygen-containing compounds having a carbinol or 0x0 group labilized by an activating group within the molecule are heated with hydrogen at elevated temperatures under pressure in the presence of a hydrogenation catalyst such as nickel. For example, Adkins on page 69 in his book on Reactions of Hydrogen, The University of Wisconsin Press, Madison, Wisconsin (1937), points out that benzyl alcohol is converted almost quantitatively to toluene by heating over nickel at 100 to 125 C. and that ethyl benzoate yields toluene at 250 C. over a copper-chromium oxide catalyst (page 101). Acetophenone over nickel at 175 C. yields ethylbenzene (page 71). Attempts to effect a similar hydrogenolysis on compounds containing either carbinol or 0x0 groups in non-labilized condition have either been unsuccessful or else have given indifferent yields of the desired hydrocarbon.

It is an object of this invention to provide a method for the hydrogenolysis of selected classes of oxygenated compounds free from aromatic unsaturation. A further object is to provide a method for the catalytic hydrogenolysis of cycloaliphatic alcohols, aldehydes and ketones to compounds having the same carbon skeleton as the starting material. A still further object is to provide a method for the catalytic hydrogenolysis of cycloaliphatic alcohols, aldehydes and ketones containing the hydroxyl or 0x0 grouping in a non-labilized condition and obtaining therefrom high yields of hydrocarbons having the same carbon skeleton as the starting material. Other objects will appear hereinafter.

These objects are accomplished by the following invention of a catalytic hydrogenolysis process which comprises passing'over a platinum catalyst at a temperature above 140 0., hydrogen and in the vapor phase a, member selected from the group of oxygenated compounds free from aromatic unsaturation consisting of cycloaliphatic alcohols, aldehydes and ketones and obtaining a compound therefrom having the same carbon skeleton as the oxygenated compound passed over said platinum catalyst. It has now been discovered that the hydrogenolysis of cycloaliphatic alcohols, aldehydes and ketones containing the hydroxyl or 0x0 groupings in nonlabilized condition can be smoothly carried out to give good yields of the desired hydrocarbons by eifecting the reaction in the vapor phase over a platinum catalyst at a temperature in excess of C. More particularly it has been found that by reacting a cycloaliphatic alcohol, aldehyde, or ketone in the vapor phase with hydrogen at a temperature in excess of 140 C. over a platinum catalyst at essentially atmospheric pressure there are obtained in high yields hydrocarbons having the same carbon skeleton as the parent materials.

In practice it has been found that the reaction is conveniently efiected by passing a gaseous mix,- ture of the cycloaliphatic alcohol, aldehyde, or ketone and hydrogen continuously at essentially atmospheric pressure over a platinum catalyst heated to between 140 C. and 350 C. As a rule, a mixture of the cycloaliphatic aldehyde, ketone or alcohol and hydrogen is passed into a chamber heated to a temperature near that selected for eifecting the reaction, and the heated gas mixture so obtained is then passed into a chamber containing the catalyst maintained at the selected reaction temperature, where the exothermic hydrogenation occurs. The gas stream is cooled, the organic product is separated and the unreacted hydrogen, if desired, re-cycled into the system.

The examples which follow illustrate more particularly the practice of this invention.

Example I A catalyst is prepared by dissolving a quantity of chloroplatinic acid equivalent to 1.5 g. of platinum in ml. distilled water. Coconut charcoal of convenient lump size, e. g., 4-14 mesh, is purified by heating in a stream of hydrogen at 450 C. for approximately twenty hours, followed by heating at 100 C. in 10% nitric acid for six hours. The charcoal then is washed with distilled water, dried at 100 C., and the last traces of nitric acid are removed by heating the charcoal for one hour at 450 C. in a stream of nitrogen. The chloroplatinic acid solution is poured over 150 ml. of the purified charcoal and the mixture is evaporated to dryness on a steam bath. An apparatus for vapor phase hydrogenolysis consists of a Pyrex U-tube, 22 mm. 0. D., immersed to a depth of 10 inches in a bath of liquid boiling at the temperature chosen for conducting the reaction. Hydrogen and the ketone, aldehyde, or alcohol are fed downward into one leg of the U-tube, which contains Pyrex helices or granular charcoal packing. The mixture of vapors then passes upward through the other legof the U-tube which contains 50 m1. of the ver'sionjfl III-g.- cyclohexanol; and ing 'material.

platinum catalyst. The products are taken off above the catalyst thru a water-cooled condenser Example J I Cyclohexanone is treated withhydro'gen "a r C. using the catalyst and apparatus describeddn' Example I. At a feed rate of -5-l0 g. cyclohexanone per hour and 160 l./hour excess hydrogen, there is obtained over a period of six hours a product consisting of awater layer anda'layer of organic liquids. Distillation of the organic material yields 10.2 g. cyclohexane, a" 30%-:ecn-

' 320 g.' hig'h' b'oi1 "Operation at-tempraturesbelow 140 rails to yield cyclol ie'x'an'e; the chief product 1 isolated 'atth lower temperatures is cycloh'exanol.

ExdmpZe'TIII V Cyclohexancl' is passedov'erthe i'catalyst ade- 4 in the case of the aldehydes and ketones two moles of hydrogen per 0X0 group are required. In actual practice, however, larger amounts are remployed 'to-aidyin the vaporizatiorr the alcohol, ketonei oraldehyde, to insure/complete "reaction, and. also to aid in the removal of the exothermic heat of reaction.

. I n practice t is necessary to employ very -fllcientcontf Hglheans to recover the hydro- 10 g'eiioly )4 carried over by the excess hydrogen, a d also to recirculate the hydrogen actorg in order to insure complete ialues. In the laboratory it is V hese conditions and. therefore 15"it"'isto be iindeis'tood that the yields given in the :examplesare lower than the actual yields under the-"conditions used due to loss of product in the efii uent hydrogen.

"Anysuitable platinum catalyst may be used in the practice of thisimfention. Thus, there may be "fsed' irgietallic "platinum-or any of its st; r'id's'siic'h'as the'oxide;chloride? ydrochl and' thlike; either unsupported or supp-6 such materials as charcoal, alumina, si1ica-,=aiid tlie" ring perates 51 bemie u scribed. in Example I at 155 CJat-aieed rate of 7-10 g.'-per hour with IBOL/hour' excess hydrogen. The product obtained "over a' period: "ofi'six and one-half hours consists of water and-a layer: of organic liquids. -Dist'illation-of the-organicnla t'erial yields 29 g. cycloh'exana':ccrresporidin sto i "72% conversion, and 2.2 g. unreacted 'cyclohexanol. Substantially identical results a are i obtained 'with' -cyclohexanol' at higher temperaturesi :but

nc reaction occurs at temperaturesbelow lilo C. Z

Example I Tetrahydroe2-furanpentanol ispassed overthe catalyst described in Exampleyl-at a temperature at atmospheric pressure;

Although the examples. haveillustrated specific conditions'of "catalyst concentration; space velocity, temperature; duration of reacticn,'etc.,itis to beunderstood that these-may be varied somewhat since the co'nditi'onsof each'texperimentf are 'determined by the particular compound be'ing reacted, the temperature employed; etc.

"In general the hydrogenolysis is V effected-tat The Z-amyltetrahydropressures *which are essentiallyatmosphenc and 3-1 s s'ir'ed', pressures whichare slightly'bel'ow'o'i above --atmospheric' may be used.

"The amount ct -hydrogen employed depends upon the particular 5 compound being treated. Thus, in the case oflthe 'al'cohols one molez i'i hydiogen' iper earbinot group'isrequired whereas pressu'reja'n high-yields is to be understood that this invention is not limited to the specific embodiments thereof except as defined in the appended claims.

We claim:

1. A catalytic hydrogenolysis process which comprises heating a member selected from the group of oxygenated compounds consisting of cycloalkanols, cycloalkanals and cycloalkanones to a temperature sufficient to vaporize the same, passing under essentially atmospheric pressure a gaseous mixture consisting of said vaporized oxygenated compound and added hydrogen continuously over and in vapor phase contact with a platinum catalyst at a temperature between 140 and 350 C., cooling the gaseous products, and separating therefrom a cycloalkane having the same carbon skeleton as said oxygenated compound.

2. A catalytic hydrogenolysis process as set forth in claim 1 in which said oxygenated compound is a cycloalkanol.

3. A catalytic hydrogenolysis process as set forth in claim 1 in which said oxygenated compound is a cycloalkanone.

4. A catalytic hydrogenolysis process as set forth in claim 1 in which said oxygenated compound is a cycloalkanal.

5. A catalytic hydrogenolysis process which comprises heating cyclohexanone to a temperature suificient to vaporize the same, passing under essentially atmospheric pressure a gaseous mixture consisting of said vaporized cyclohexanone and hydrogen continuously over and in vapor phase contact with a platinum catalyst at a temperature from 150 to 300 0., cooling the gaseous products, and separating therefrom cyclohexane.

6. A catalytic hydrogenolysis process which comprises heating cyclohexanol to a temperature suflicient to vaporize the same, passing under essentially atmospheric pressure a gaseous mixture consisting of said vaporized cyclohexanol and hydrogen continuously over and in vapor phase contact with a platinum catalyst at a temperature from to 300 C., cooling the gaseous products, and separating therefrom cyclohexane.

JOHN E. CASTLE. BENJAMIN W. HQWK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date Ford et a1. May 4, 1948 OTHER REFERENCES Number 

1.A CATALYTIC HYDROGENOLYSIS PROCESS WHICH COMPRISES HEATING A MEMBER SELCETED FROM THE GROUP OF OXYGENATED COMPOUNDS CONSISTING OF CYCLOALKANOLS, CYCLOLKANALS AND CYCLOALKANONES TO A TEMPERATUE SUFFICIENT TO VAPORIZE THE SAME, PASSING UNDER ESSENTIALLY ATMOSPHERIC PRESSURE A GASEOUS MIXTURE CONSISTING OF SAID VAPORIZED OXYGENATED COMPOUND AND ADDED HYDROGEN CONTINUOUSLY OVER AND IN VAPOR PHASE CONTACT WITH A PLATINUM CATALYST AT A TEMPERATURE BETWEEN 140* AND 350* C., COOLING THE GASEOUS PRODUCTS AND SEPARATING THEREFRO A CYCLOALKANE HAVING THE SAME CARBON SKELETON AS SAID OXYGENATED COMPOUND. 